Abstract
In this paper, a terahertz hyperspectral imaging architecture based on an electro-optic terahertz dual-comb source is presented and demonstrated. In contrast to single frequency sources, this multi-heterodyne system allows for the characterization of the whole spectral response of the sample in parallel for all the frequency points along the spectral range of the system. This hence provides rapid, highly consistent results and minimizes measurement artifacts. The terahertz illumination signal can be tailored (in spectral coverage and resolution) with high flexibility to meet the requirements of any particular application or experimental scenario while maximizing the signal-to-noise ratio of the measurement. Besides this, the system provides absolute frequency accuracy and a very high coherence that allows for direct signal detection without inter-comb synchronization mechanisms, adaptive acquisition, or post-processing. Using a field-effect transistor-based terahertz resonant 300 GHz detector and the raster-scanning method we demonstrate the two-dimensional hyperspectral imaging of samples of different kinds to illustrate the remarkable capabilities of this innovative architecture. A proof-of-concept demonstration has been performed in which tree leaves and a complex plastic fragment have been analyzed in the 300 GHz range with a frequency resolution of 10 GHz.
Highlights
In this paper, a terahertz hyperspectral imaging architecture based on an electro-optic terahertz dual-comb source is presented and demonstrated
Solid-state electronic terahertz sources based on direct signal generation o scillators[12] and on synthesized signal generators with frequency multipliers using either diode technology[13] or MMIC technology[14]
Several proof of principle experiments have been carried out to validate the performance of the proposed hyperspectral imaging system
Summary
A terahertz hyperspectral imaging architecture based on an electro-optic terahertz dual-comb source is presented and demonstrated. The frequency-domain approach is based on photonic continuous-wave (CW) difference frequency THz generation and employs photoconductors covering the frequency range of up to almost 3 T Hz11 This method provides a far higher spectral resolution and accuracy, and a roughly similar dynamic range. Solid-state electronic terahertz sources based on direct signal generation o scillators[12] and on synthesized signal generators with frequency multipliers using either diode technology[13] or MMIC technology[14] These sources exhibit very high spectral resolution, very fast tuning capabilities and output power levels exceeding those of photonic systems. They are restricted to a limited frequency bandwidth due to the different waveguide bands. Many challenges still have to be faced to reach the same level of maturity as solid state THz generators, THz QCLs are a promising approach especially at higher THz frequencies with a performance that is expected to noticeably improve in the decades to come
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